Aerosol cans have either a one-part or multi-part design. In the case of one-part aerosol cans made of aluminum, the cylindrical can body is produced by cold sinking. Subsequently, a valve seat is formed at the open end by means of compressive necking down. This type of production process is very expensive and involved as a result of the equipment requirements for the many processing steps, as well as the water and energy requirements for cleaning and drying. Patent documents U.S. Pat. No. 4,095,544 and EP 0 666 124 A1 describe the production of seamless steel cans, wherein a cylindrical can body is manufactured from a steel sheet coated with tin or plastic material by punching, pressing and ironing. It has turned out that enormous problems occur with forming restricted neck portions, because the material structure is changed and/or hardened by the ironing. Also widely used are cans made from sheet steel for which the shell has a longitudinal welding seam. The bottom and the upper closure are attached to the can shell by folded seam connections. With folded seam connections sealing problems can occur which, for example, are reduced with the aid of sealing rings. With the standard cans having extremely thin walls problems occur with seals that are arranged at the end faces. Two-part or multi-part cans are known from documents EP 200 098 A2 and EP 208 564, for which the parts are joined by means of laser welding. The can shape that is predetermined by the known laser-welded seams in the connecting regions between can wall and bottom and/or valve seat is very unattractive. In addition, no cost-effective production with sufficiently high piece numbers is possible with the known methods. The above-mentioned longitudinal welding seams, particularly those described in document U.S. Pat. No. 4,341,943, have small offsets and/or thickness differences in peripheral direction, which can lead to problems during the welding-on of the closure members.
A valve seat is provided on the can body for securing valves on aerosol cans. A connecting bowl is crimped onto the valve seat together with the valve. Hairline cracks will form on the valve seat if the valve seat is formed by necking down and reshaping the can shell, which can lead to undesirable microscopic leaks following the crimping on of the connecting bowl. Hairline cracks can also occur on a valve seat that is formed onto a closure member, separately from the can shell. Even if no hairline cracks appear, the crimping on of the connecting bowl to the valve seat represents an involved processing step. In addition, a valve seat with standard diameter is used for aerosol cans with differently large diameters, meaning a minimum can diameter must be maintained for small cans.
Aerosol cans are described in International Application WO 00/35772, for which the closure member is welded together with the valve onto the can shell by forming a laser welding seam. Document FR 2 543 923 describes a can, for which a can closure member is attached together with the valve seat by means of laser welding to the can shell. The above-described solutions for the welding seams comprise flanges and/or seam contact regions that are cylindrical or project radially outward, relative to the can axis, thereby resulting in an unattractive appearance for the cans. The end faces of the two flanges to be joined project outward from the can body during the welding. The reshaping of the flanges following the welding operation is extremely involved because the welding seam generates high form stability at the flanges. Even reshaped flanges are undesirable for many aerosol cans, for example in the cosmetics field, in particular for cans with small diameters.